The Viruses They are a Changin: On The Eco-evolutionary Dynamics of Virus-Host Interactions

Viruses are ubiquitous in the environment, with densities often ten-fold higher than that of their microbial hosts. Viruses can function like microbial predators, regulating the amount and diversity of hosts present in a community. However, efforts to understand the dynamics of complex virus-microbe communities are still in their infancy. Here, I present examples of the interplay between evolutionary and ecological dynamics arising due to virus-microbe interactions. In the first example, I show how rapid changes in the frequency of bacterial strains that differ in their susceptibility to infection can imprint a novel ecological signature - so-called cryptic dynamics.  Then, in a second example, I show how rapid changes in the frequencies of hosts and viruses that differ in their cross-infectivity can reverse the canonical predictions of Lotka-Volterra (and similar) dynamics, leading to dynamics in which it appears that hosts eat viruses. In both examples, I synthesize insights from theory and models with results from laboratory experiments.  However, applying such insights to the environment requires addressing an ongoing challenge: how to characterize who infects whom when many ubiquitous microbes and associated viruses are not yet culturable.  I close with a discussion of recent innovations that can help shed light on the interactions of viruses and microbes using culture-independent techniques.